With recent rapid progress of information transmitting systems, silver halide photographic light sensitive materials have been increasingly required to have high sensitivity. Such systems are, for example, high speed phototypesetting systems according to which information output from an electronic computer is immediately displayed as letters or figures by a cathode ray tube and press facsimile systems for rapid transmission of news paper originals to remote places.
Photographic phototype setting materials include photographic films and papers used in a process for preparing a lithographic printing plate and silver salt diffusion transfer, called DTR-based lithographic printing plates disclosed in e.g. U.S. Pat. No. 4,501,811 and U.S. Pat. No. 4,784,933. With the latter materials a lithographic printing plate is immediately obtained without the need of a contact exposure or camera exposure.
Todate on the market phototypesetters usually work with a He/Ne laser (632 nm), a laser diode (680 nm) or LED ( 670 or 780 nm). Especially phototypesetters that operate with a He/Ne laser or LED (670-680 nm) are frequently employed. Since these light sources emit in a very narrow spectral range photographic materials were developed for each of the above mentioned light sources.
A disadvantage of all these materials is that they are sensitive to visible light and have to be treated in a dark room. Recently, there are available lasers which emit in the spectral range of 390-410 nm. Materials, sensitive for said lasers could have the possibility of being treated in subdued yellow light.
However, when said deep blue lasers are used to irradiate an imaging element comprising in the order given on a hydrophilic surface of a support (i) an image receiving layer containing physical development nuclei, (ii) a photosensitive layer containing at least one silver halide emulsion in water permeable relationship with said image receiving layer and spectrally sensitized for said laser, the imaging element can still not be treated under subdued yellow light without an unwanted increase in sensitivity, leading to an irreproducible sensitivity and possibly fog.